Different types of tools are used to perform hundreds of processing operations during semiconductor device fabrication. Most of these operations are performed in process chambers at very low pressure, i.e., in a vacuum or partial vacuum. Such process chambers may be arranged about a central hub, and the hub and process chambers may be kept at substantially the same very low pressure. Wafers may be introduced to the process chambers by wafer handling systems that are mechanically coupled to the process chambers. The wafer handling systems transfer wafers from the factory floor to the process chamber. The wafer handling systems may include load locks to bring the wafers from atmospheric conditions to very low pressure conditions and back, and robotic arms equipped with end effectors configured to support the wafers during wafer transport.